A transmitter used in communication and broadcasting equipment such as a mobile telephone system or a wireless LAN device is required to operate so that its power consumption is low while maintaining a highly accurate transmission waveform without depending on the amount of transmission power. In particular, a transmission power amplifier, which is provided at the last stage of the transmitter, consumes a large amount of power. Therefore, the transmission power amplifier is required to have a high power efficiency.
Recently, a switching amplifier has been focused on as a power amplifier in which a high power efficiency can be expected. The switching amplifier is assumed to receive a pulse waveform signal as an input signal, thus achieving power amplification while maintaining its waveform. A pulse waveform signal amplified by the switching amplifier is adequately suppressed in frequency components other than a desired frequency component by a filter element and then the resulting signal is emitted from an antenna.